# How many counterterms does QED have?

I have read the statement that QED has four counterterms to cancel divergences. However, I have learnt that there are only three counterterms (vertex, electron propagator, photon propagator), which is consistent with this PDF$$^1$$ (42KB).

But then, the last page of this PDF$$^2$$ (229KB) states that there are five kinds of diverging skeleton diagrams in QED, one of which vanishes (the triangle).

Is there a fourth counterterm or did the original statement actually refer not to counterterms, but to diverging diagrams?

$$^1$$ "QED Feynman Rules in the Counterterm Perturbation Theory" by Vadim Kaplunovsky (University of Texas)

$$^2$$ "Renormalization in QED" (Imperial College London)

• Makes perfect sense. In the first PDF I've linked, there are only three diagrams, but they depend on four parameters: $\delta_1$, $\delta_2$, $\delta_m$ and $\delta_3$. – Stephan Nov 11 '18 at 10:12